CONTINUOUSWAVE

My 1987 SUPER SPORT 15 has been re-powered with a [2021-production epoch Mercury] 60-HP engine.

What is the best engine mounting height?

What is the best propeller?

Should I buy an aluminum propeller?

What is the gear ratio of the engine?

What is the maximum recommended engine speed in RPM?

What is the weight of the engine?

As a starting point for engine mounting height, installing the engine at one-hole-up from lowest is a safe initial point. Some enthusiasts will recommend starting at two-holes-up from lowest on the basis that later having to lower the engine to one-hole-up will be easier than starting at one-hole-up and trying to raise to two-holes-up.

The engine weight is 247-lbs. Max rpm is 5500-6000. Gear ratio (standard gear case) is 1.83:1

Owners with the classic 15 Super Sport with a Mercury 60 FourStroke with the 1.83 lower unit, the recommended prop includes:

13 3/8 x 12 Vengeance

The engine should be mounted 1 hole up meaning the top engine bolts are in the second hole down from the top.

Thanks so much Phil. Is the Vengance a stainless prop, I was thinking aluminum.

Ed

boatsmith wrote:The engine weight is 247-lbs. Max rpm is 5500-6000. Gear ratio (standard gear case) is 1.83:1

An engine weight of 247-lbs is a reasonable weight for a 15-foot hull. Compare at

http://continuouswave.com/ubb/Forum4/HTML/002449.html

Using 5750-RPM (the middle of the recommended maximum engine speed range) and a gear ratio of 1.83:1, with a 12-pitch propeller (as suggested above) the boat speed would be about 32.5-MPH.

That seems a bit slow for a 60-HP engine. My 15-footer with an old 50-HP )that was not rated at the propeller shaft but at the engine crankshaft so maybe 45-HP) could hit about 34-MPH. On that basis. although your 15-footer is probably heavier overall with the additional interior weight and engine weigh. your 60-HP ought to be able to obtain at least 34-MPH.

Looking at 34.5-MPH for a top speed, the pitch calculation is 12.7. A 13-pitch propeller would be another option. In propellers for smaller engines, the pitch is often available in one-inch increments.

Ed -

The recommendation for aluminum propellors is no longer valid with the introduction of modern hub designs and advanced materials.

While less expensive, an aluminum prop is more prone to damage resulting in "repair", tuning or replacement. A Mercury Vengence stainless steel prop will outlast your engine. The stainless steel props are also more efficient and produce better performance, hence the recommendation.

I use the analogy - installing an inexpensive prop on an outboard engine is like installing Radio Flyer wagon wheels on a Ferrari.

Wow I would not have thought a 12" prop. That boat should do over 40mph with a 60hp.